Sex question

As a back story i am usually very horny and want to have sex with my boyfriend alot. I also dtarted the dopaprovera shot back in april. Him and i have been together for almost 2 years and sex has never been uncomfortable unless I had bv or yeast and didnt know till after. My boyfriend and I dont really have sex any more well go like one time every two weeks. Im not as horny anymore i think from the shot and ive been really dry down there. Recently weve been using a lube from walmart bc i could afford the one I like that we usually use as it got expensive to keep buying them. It was alright at first but recently sex has been a bit uncomfortable and my vagina gets that sensitive feeling. And after sex i get a burning sensation down there and feel pulse. Idk why what could it be and how do i stop it i just want to enjoy sex again without it being uncomfortable. My vagina opening is sensitive to touch and very dry I have to make an annual bc i missed my appointment and talk to dr to switch back to pill bc of the weight gain from the shot but could it be the shot causing this